Industrial robots, especially multi-articulated industrial robots are installed at various positions depending on environmental conditions at a site where the industrial robots are used. For example, when a multi-articulated industrial robot is used for a welding operation and various sealing operations, the robot is often installed on the surface of a wall or a ceiling of a building instead of a ground floor, to be able to assume a posture suitable for these operations. When these positions of installation of robot units are taken with a multi-articulated industrial robot having a plurality of articulated robotic arms, load conditions due to gravitational forces applied to respective arms mounted on respective articulatory axes and a rotary columnar body of the multi-articulated industrial robot during movement of these movable elements of the industrial robot differ in accordance with the installed position. Namely, when the robot unit is disposed so that the robot is installed on a horizontal plane, the rotary columnar body of the robot unit rotatable about a vertical axis is not subjected to a load due to the force of gravity applied to the body. Nevertheless, when the robot unit is disposed on a vertical surface of a wall, the axis about which the columnar body thereof is rotated horizontally is extended, and therefore, during the rotating motion of the columnar body of the robot, the body must be subjected to a large change in a load depending on the position to which the columnar body per se is rotated about the rotating axis thereof, as well as the position to which the robotic arm pivotally attached to a foremost end of the columnar body is brought. As a result, sometimes the robot columnar body is subjected to an extraordinary load, and accordingly, an electric motor used as a rotatory drive source for the columnar body is subjected to an excessive load. Therefore, in the case of conventional industrial robots, when the robots are to be used at various positions, a table showing the correspondence between different sited positions and the related operating conditions about respective articulatory axes is prepared beforehand during the manufacture of the industrial robots, and the prepared table is inserted in the instructions for operating the industrial robots. Thus, users of the industrial robots are able to refer to the table when installing each robot unit at a site, and to subsequently set the operating conditions of respective movable elements of the robot in the robot control unit depending on the position of installation of the robot unit.
However, when the above-mentioned method of setting the operating conditions is taken, the user of each industrial robot must determine the position of installation of the robot unit by measuring an angle of inclination of the robot unit with respect to a horizontal ground floor, and subsequently set the operating conditions of respective articulatory axes, such as the moving region (stroke of the robotic arms), and the maximum operating speeds corresponding to the measured angle of inclination of the robot. Namely, the user must set many operating conditions in the robot control unit before using the industrial robot, which is cumbersome for the user and often causes a setting of erroneous operating conditions in the robot control unit because of a misreading of the table by the user. As a result, the industrial robot cannot be properly controlled and is not stably operated.